- 您现在的位置：买卖IC网 > PDF目录79915 > LT1871IMS-7#TR (LINEAR TECHNOLOGY CORP) SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 PDF资料下载
参数资料
| 型号： | LT1871IMS-7#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | PLASTIC, MSOP-10 |
| 文件页数： | 7/32页 |
| 文件大小： | 461K |
| 代理商： | LT1871IMS-7#TR |
第1页第2页第3页第4页第5页第6页当前第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LTC1871-7
15
18717fc
APPLICATIONS INFORMATION
Sense Resistor Selection
During the switch on-time, the control circuit limits the
maximum voltage drop across the sense resistor to about
150mV (at low duty cycle). The peak inductor current
is therefore limited to 150mV/RSENSE. The relationship
between the maximum load current, duty cycle and the
sense resistor RSENSE is:
RSENSE VSENSE(MAX)
1–DMAX
1+
2
IO(MAX)
The VSENSE(MAX)term is typically 150mV at low duty cycle,
and is reduced to about 100mV at a duty cycle of 92% due
to slope compensation, as shown in Figure 11.
It is worth noting that the 1 – DMAX relationship between
IO(MAX) and RSENSE can cause boost converters with a wide
input range to experience a dramatic range of maximum
input and output current. This should be taken into con-
sideration in applications where it is important to limit the
maximum current drawn from the input supply.
Figure 11. Maximum SENSE Threshold Votlage vs Duty Cycle
DUTY CYCLE
0
MAXIMUM
CURRENT
SENSE
VOLTAGE
(mV)
100
150
0.8
18717 F11
50
0
0.2
0.4
0.5
1.0
200
Boost Converter: Power MOSFET Selection
Important parameters for the power MOSFET include the
drain-to-source breakdown voltage (BVDSS), the threshold
voltage (VGS(TH)), the on-resistance (RDS(ON)) versus gate-
to-source voltage, the gate-to-source and gate-to-drain
charges (QGS and QGD, respectively), the maximum drain
current (ID(MAX)) and the MOSFET’s thermal resistances
(RTH(JC) and RTH(JA)).
The gate drive voltage is set by the 7V INTVCC low drop
regulator. Consequently, 6V rated MOSFETs are required
in most high voltage LTC1871-7 applications.
Pay close attention to the BVDSS specications for the
MOSFETs relative to the maximum actual switch voltage
in the application. The switch node can ring during the
turn-off of the MOSFET due to layout parasitics. Check the
switching waveforms of the MOSFET directly across the
drain and source terminals using the actual PC board layout
(not just on a lab breadboard!) for excessive ringing.
Calculating Power MOSFET Switching and Conduction
Losses and Junction Temperatures
In order to calculate the junction temperature of the power
MOSFET, the power dissipated by the device must be known.
This power dissipation is a function of the duty cycle, the
load current and the junction temperature itself (due to
the positive temperature coefcient of its RDS(ON)). As a
result, some iterative calculation is normally required to
determine a reasonably accurate value. Care should be
taken to ensure that the converter is capable of delivering
the required load current over all operating conditions (line
voltage and temperature), and for the worst-case speci-
cations for VSENSE(MAX) and the RDS(ON) of the MOSFET
listed in the manufacturer’s data sheet.
The power dissipated by the MOSFET in a boost converter
is:
PFET =
IO(MAX)
1–D
2
RDS(ON) D T
+k VO2
IO(MAX)
1–D
( ) CRSS f
The rst term in the equation above represents the I2R
losses in the device, and the second term, the switching
losses. The constant, k = 1.7, is an empirical factor inversely
related to the gate drive current and has the dimension
of 1/current. The ρT term accounts for the temperature
coefcient of the RDS(ON) of the MOSFET, which is typically
0.4%/°C. Figure 12 illustrates the variation of normalized
RDS(ON) over temperature for a typical power MOSFET.
相关PDF资料 |
PDF描述 |
|---|---|
| LX1672-06CLQTR | 1 A DUAL SWITCHING CONTROLLER, 690 kHz SWITCHING FREQ-MAX, PQCC38 |
| LM3711XKMM-463/NOPB | 2-CHANNEL POWER SUPPLY MANAGEMENT CKT, PDSO10 |
| LMX2502LQX1635/NOPB | PLL FREQUENCY SYNTHESIZER, 19.68 MHz, QCC28 |
| LM385BDE4-1-2 | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 1.235 V, PDSO8 |
| LM4040AIMX-2.5 | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 2.5 V, PDSO8 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1871IMS-7-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
| LT1873-41 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Optoelectronic |
| LT1873-41UR | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Optoelectronic |
| LT1880 | 制造商:LINER 制造商全称:Linear Technology 功能描述:SOT-23, Rail-to-Rail Output, Picoamp Input Current Precision Op Amp |
| LT1880CS5 | 制造商:Linear Technology 功能描述:OP Amp Single GP R-R O/P ±18V/36V 5-Pin TSOT-23 |
发布紧急采购，3分钟左右您将得到回复。